<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="css/bootstrap.min.css">
</head>

<style>
    .item{
        text-align: center;
    }
    .item img{
        width: 50px;
        height: 50px;
        border-radius: 50%;
    }

    @media screen and (max-width:992px) {
        .item .nickname{
            color: blue;
        }
    }

    @media screen and (max-width:768px) {
        .item .nickname{
            color: red;
        }
    }

</style>
<body>
    <!-- 
        127.0.0.1 本地IP

        www.baidu.com =>

        www
            _book
                mdbook
                index.html

        栅格系统
        媒体查询
        单位 rem px em vw vh
     -->
    <!-- Standard button -->
    <button type="button" class="btn btn-default">（默认样式）Default</button>

    <!-- Provides extra visual weight and identifies the primary action in a set of buttons -->
    <button type="button" class="btn btn-primary">（首选项）Primary</button>

    <!-- Indicates a successful or positive action -->
    <button type="button" class="btn btn-success">（成功）Success</button>

    <!-- Contextual button for informational alert messages -->
    <button type="button" class="btn btn-info">（一般信息）Info</button>

    <!-- Indicates caution should be taken with this action -->
    <button type="button" class="btn btn-warning">（警告）Warning</button>

    <!-- Indicates a dangerous or potentially negative action -->
    <button type="button" class="btn btn-danger">（危险）Danger</button>

    <!-- Deemphasize a button by making it look like a link while maintaining button behavior -->
    <button type="button" class="btn btn-link">（链接）Link</button>

     <!-- 固定宽度的布局容器 -->
    <div class="container">
        <!-- 栅格的行 -->
        <div class="row">
            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>

            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>

            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>

            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>
            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>
            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>
            <div class="col-md-3 col-sm-4 col-xs-12">
                <div class="item">
                    <img src="images/1.jpg" alt="">
                    <div class="nickname">demo</div>
                </div>
            </div>
        </div>
    </div>
</body>

</html>
<script src="js/jquery-3.7.1.min.js"></script>
<script src="js/bootstrap.min.js"></script>